Armor of Agathys

Duration: 1 hour
A protective magical force surrounds you,
manifesting as a spectral frost that covers you
and your gear. You gain 5 temporary HP. If a
creature hits you with a melee attack while you
have these HPs, the creature takes 5 cold damage.
At Higher Levels. For each extra spell slot, both
the temporary HPs and the cold damage increase
by 5.